The present invention relates to a method of controlling the flow rate of air intake of an internal combustion engine, particularly as it relates to an air intake control method during the idling condition.
There is known a method of controlling the air intake of an internal combustion engine when a throttle valve disposed in an intake passage is at the fully closed position. According to this conventional method, the flow rate of intake air, when the throttle valve is fully closed, is controlled by adjusting a control valve disposed in an air bypass passage which communicates with the intake passage on opposite sides of the throttle valve. Such an air intake control method is usually employed for controlling the idling rotational speed of the engine. The idling rotational speed can be controlled by a closed loop if the bypass control valve is adjusted to conrol the flow rate of the air sucked into the engine through the bypass passage so that the detected actual rotational speed of the engine becomes equal to the desired idling rotational speed.
However, according to the conventional air intake control method, the position of the bypass control value is always maintained at a valve equal to an optimum openin degree in a stable idling condition, even when the engine is in the starting condition. Therefore, if the throttle valve is at the fully closed position, a sufficient flow rate of intake air cannot be obtained during starting and just after starting, causing the rotational speed to be slow. As a result, difficulty in starting the engine may sometimes occur. Furthermore, if the engine runs slowly even after starting, the driver will feel uneasy about the start of the engine. This is because the driver usually recognizes that the rotational speed of the engine is high when the engine is first started. The engine may sometimes stall if a large load is applied to an engine which is running slowly, just after starting.